Research indicates that youth with autism spectrum disorder often experience unmet health care needs and receive poorer quality of care. Intellectual disability commonly co-occurs with autism spectrum disorder; however, the nature of unmet health care needs and health care quality in youth with autism spectrum disorder and intellectual disability have not been investigated. As such, this study sought to examine associations among co-occurring intellectual disability, unmet physical and mental health care needs, and health care quality in youth with autism spectrum disorder. Data from this study were acquired from the 2016-2018 National Survey of Children's Health, a nationally distributed caregiver-report questionnaire. Results found that the frequency of unmet mental health care need was significantly higher among children with autism spectrum disorder with co-occurring intellectual disability than those without intellectual disability. Using a structural equation modeling approach, it was found that the total effect of co-occurring intellectual disability on composite health care quality was significant. Investigation of indirect effects indicated that unmet mental health care need mediated the relationship between co-occurring intellectual disability and health care quality. These findings suggest that youth with autism spectrum disorder and co-occurring intellectual disability may be more likely to experience unmet mental health care needs, and that their unmet mental health care needs may negatively impact their health care quality.